1. Field of the Invention
The present invention generally relates to a magnetic tape recording and reproducing apparatus which is of a so-called one-way type for reproducing only one side of a cassette pack tape, and more particularly to an improved magnetic tape reproducing apparatus which can automatically proceed, when the end of tape is detected, to a subsequent operation such as stopping of the drive motor, ejection of the cassette pack or reproduction of the tape from the beginning.
2. Description of the Prior Art
The magnetic tape recording and reproducing apparatuses include two well-known types: an automatic-return type for automatically reproducing both sides of a cassette pack tape successively, and a one-way type for reproduction of only one side of a cassette pack tape.
When a magnetic tape in a cassette pack being played reaches the end of tape in the case of a one-way type magnetic tape reproducing apparatus, it is necessary to stop the drive motor for putting the apparatus as a whole out of operation, or to eject the cassette pack for reproducing another cassette pack tape. In the case of a magnetic tape recording apparatus in which normally the drive motor is only stopped but no ejection of the cassette pack is done, or in which ejection of the cassette pack is done under the action of a spring or the like, a change of tape tension at the tape end is detected for stopping the drive motor. In the case of a magnetic tape reproducing apparatus of a so-called automatic-ejection type in which the cassette pack is automatically ejected as driven by the drive motor, the stop of reel base rotation is detected by electrical means such as a proximity switch and photocoupler, or by other mechanical means, for thereby switching the driving force of the motor from the reel base side to the ejection mechanism, thus ejecting the cassette pack, and then the motor is stopped.
Heretofore, it has been proposed to utilize the friction between the reel bases and their respective associated rotation detecting discs for mechanically detecting the stopped rotation of the reel bases in order to detect the end of tape as discussed above.
As shown in FIG. 1, such a device for detection of the end of tape comprises a rotation detecting disc or member 3 fitted on the outer circumference of a boss 2, in friction therewith, the boss 2 being formed integrally with a reel base 1, and the disc 3 having a protrusion 4 thereon. The disc 3 has further formed therein a Y-shaped guide slot 5, between two upper segments of which the protrusion 4 is located, and in which there is oscillatably fitted a pin 7 provided at one end 6a of an oscillating plate 6 which is separately supported. The oscillating plate 6 is rotatably supported to a support shaft 8, and also coupled at the other end 6b thereof with a well-known stopping mechanism and tape reverse mechanism (not shown) which are actuated as a result of the detection of the end of tape.
Furthermore, the oscillating plate 6 is oscillated by a cam 9 which is rotated under the effect of the driving force of the motor, in such a manner that the pin 7 is moved reciprocally within the Y-shaped guide slot 5. Particularly, the cam 9 is provided near the center of a pulley 10 normally driven by the motor, and as a cam follower pin 11 provided at the end 6b of the oscillating plate 6 moves along the circumferential surface of the cam 9, the pin 7 moves, as shown in FIG. 1, between the branching point and the end of each branch thereof. Also, the pulley 10 has provided at the outside thereof an island cam 12 which is separate from the cam 9. As shown, in FIG. 2, when the cam follower pin 11 moves over the circumferential face of this island cam 12, the pin 7 moves reciprocally from the base of the Y-shaped guide slot 5 to the branching point thereof (namely, the end of the protrusion 4).
Note that there is provided between the oscillating plate 6 and the chassis of the magnetic tape reproducing apparatus a spring 13 which forces the cam follower pin 11 toward the surfaces of the cam 9 and island cam 12.
In this prior-art magnetic tape reproducing apparatus, the end of tape is detected in the following manner:
First, while the tape is running, the reel base 1 is rotating as shown in FIG. 2, and the rotation detecting disc 3 which is frictionally engaged with the boss 2 is urged by the reel base 1 in the rotating direction thereof, for example, in the direction of arrow as shown. One of the branches of the Y-shaped guide slot 5 will take the same direction as the orbit delineated by the oscillating plate 6. Therefore, the oscillating plate 6 will be caused, by the cam follower pin 11 being normally-in contact with the rotating cam 9, to repeatedly move over a short distance equivalent to the length of the one branch of the Y-shaped guide slot 5. Since the end of tape is not yet reached while such a small oscillation is being repeated, the stopping and tape reverse mechanisms operationally connected with the oscillating plate 6 are not activated.
On the other hand, when the end of tape is reached and so the reel base 1 stops rotating, the rotating detecting disc 3 is no longer urged in the direction of the arrow. Thus, as the pin 7 attempts to move into a branch of the Y-shaped guide slot 5 under the action of the cam 9, it will abut the protrusion 4 between the branches so as to become incapable of getting into any of the branches of the slot 5. It should be noted that in case the reel base 1 then rotates and the rotation detecting disc 3 is applied with a frictional force, the pin will be able to enter either of the slot branches since even the abutment of the pin 7 on the protrusion 4 causes the disc 6 to immediately escape in the direction of arrow.
As the pulley 10 keeps rotating even after the oscillation of the plate 6 is suspended by the abutment of the pin 7 on the protrusion 4, the cam follower pin 11 will leave the circumferential surface of the cam 9. That is, as the circumferential surface of the cam 9 approaches the center of the pulley 10, the pin 7 of the oscillating plate 6 moves toward the branches of the Y-shaped guide slot 5. However, when the pin 7 gets engaged with the protrusion 4, the cam follower pin 11 cannot follow the cam 9 any longer. As the pulley 10 keeps rotating in such conditions, the cam follower pin 11 will abut the circumferential face of the island cam 12 which in turn will force the oscillating plate 6 to start oscillating in the opposite direction. The island cam 12 will further cause the pin 7 to reciprocally move between the protrusion 4 and the end of the stem or base of the Y-shaped guide slot 5. In this way, the oscillating plate 6 will oscillate a greater stroke as compared with that while the tape is running. This increased oscillation is used to determine the end of tape and thus actuate the motor stopping and cassette ejection mechanisms operationally coupled with the oscillating plate 6.
However, use of such prior-art mechanical tape-end detection device utilizing the friction in the one-way type magnetic tape reproducing apparatus incurs the following various problems:
As well known, in a magnetic tape reproducing apparatus, the tape is made to run in the following three modes: Reproduction or playing mode; fast-forward mode for fast forwarding the tape in the same direction as for tape reproduction; and rewind mode for fast run of the tape in the opposite direction to that for tape reproduction. Among these modes of tape run, the reproduction and fast forward modes make it necessary that when the trailing end of the tape is reached, the cassette or cassette pack should be ejected and the user should turn the cassette from one side to another and insert it back into the magnetic tape reproducing apparatus. In the rewind mode, the cassette need not be turned as in the above, but the tape must be reproduced in the reproduction mode from the beginning end of the tape.
However, in the prior-art magnetic tape reproducing apparatus described with reference to FIG. 1 and FIG. 2, both the trailing end and beginning end of a tape are similarly detected as a tape end, and even in case no ejection of the cassette is necessary, as in the rewind mode, the ejection mechanism will be actuated as in the other modes, namely, in the reproduction and fast-forward modes. Thus, the user has to insert the ejected cassette as it is back into the magnetic tape reproducing apparatus in order to restore the reproduction state. Such operations have been a great nuisance to the users.
Furthermore, the use of a mechanical tape-end detection device utilizing friction, as described and illustrated in the foregoing, in a magnetic tape reproducing apparatus of a so-called automatic-loading type into which a cassette pack is loaded by the driving force of the drive motor, the following problems result:
Loading of a cassette pack into the magnetic tape reproducing apparatus under the effect of the driving force of the drive motor makes it necessary to turn on the power on-off switch and start the motor when the cassette pack has been inserted a little into the cassette insertion opening of the apparatus.
It will take a certain length of time until the cassette pack is pulled in and fully loaded into the apparatus under the action of the motor thus started.
For this reason, when the reproduction head is pressed to the tape and the pinch roller is pressed to the capstan after the cassette pack is loaded into the apparatus in the automatic mode, the tape will already have been made to run by the reel base, to which the revolution of the motor is transmitted at the same time as the powering of the apparatus, with the result that the reproduction will not be started at a correct position of the tape. Especially in case a cassette pack tape is used on which starts of records or selections are preset in respective start positions by indexing, such start of reproduction at an incorrect position results in missing of such record starts.
Generally, a prior-art magnetic tape reproducing apparatus adopts, to avoid the above-mentioned inconvenience, an arrangement in which an idler or the like is used to keep stopping the reel base without transmission of the driving force of the motor thereto until the head and pinch roller are completely pressed to the tape and capstan, respectively. Use of the frictional-type tape end detecting device described with reference to FIG. 1 in a such magnetic tape reproducing apparatus will, however, result in occurrence of a tape end detection since the reel base is not rotated. As the result, the stopping mechanism is actuated to make the head and pinch roller move in the opposite direction to that for run of the tape, the cassette pack is ejected following the acutuation of the stopping mechanism, which however depends on the type of magnetic tape reproducing apparatus used, or the tape run is reversed, resulting in no reproduction of any intended program or record on the tape. Also if the tape is slackened within the cassette tape, it may possibly be wound on the pinch roller or capstan. To avoid this, the take-up reel base should preferably be rotated to unslacken the tape before the latter is pressed to the head and pinch roller. However, in the case of a magnetic tape reproducing apparatus in which an idler is used to isolate the reel base from the driving force of the motor, the tape cannot be unslackened.